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An FTP secure client library for C#

, 10 Dec 2008 CPOL
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How to implement an FTP secure connection with an SSL stream class.

Introduction

The purpose of this article is to create a C # FTP client in Secure mode, so if you don’t have much knowledge of FTPS, I advise you to take a look at this: FTPS.

In the .NET Framework, to upload a file in FTPS mode, we generally use the FtpWebRequest class, but you can not send commands with « quote » arguments, and even if you search on the web, you will not find a concrete example of a secured C# FTP client.

It’s for those reasons I decided to create this article.

SSL Stream?

To send a socket in Secure Socket Layer (SSL) mode, we use the class System.Net.Security.SslStream.

Provides a stream used for client-server communication that uses the Secure Socket Layer (SSL) security protocol to authenticate the server and optionally the client”.

For more information, refer to MSDN.

Using the Code

1. Pre-Authenticate

FTPFactory ftp = new FTPFactory();
ftp.setDebug(true);
ftp.setRemoteHost(Settings.Default.TargetFtpSource);

//Connect to SSL Port (990)
ftp.setRemotePort(990);
ftp.loginWithoutUser();

//Send "AUTH SSL" Command
string cmd = "AUTH SSL";
ftp.sendCommand(cmd);

Before connecting to the FTP server in SSL mode, you have to define the 990 SSL port and send the « AUTH SSL » command authentication using SSL.

WelcomeFTPSecure.JPG

2. Create SSL Stream

//Create SSL Stream
ftp.getSslStream();
ftp.setUseStream(true);
//Login to FTP Secure
ftp.setRemoteUser(Settings.Default.TargetFtpSecureUser);
ftp.setRemotePass(Settings.Default.TargetFtpSecurePass);
ftp.login();

ftp.getSslStream() creates an SSL stream from client socket which will be used for exchange between the client and the server FTPS. Then, you have to enter a login and password to authenticate on the FTPS server.

Note: if the SSL stream is well established, then I display all the information about the server certificate.

CertificatInfos.JPG

3. Upload File

//Set ASCII Mode
ftp.setBinaryMode(false);

//Send Arguments if you want
//cmd = "site arg1 arg2";
//ftp.sendCommand(cmd);

//Upload file
ftp.uploadSecure(@"Filepath", false);

ftp.close();

Before uploading a file, you have to specify the mode: ftp.setBinaryMode(bool value).

  • value is false --> ASCII mode
  • value is true --> Binary mode

By default, it’s binary. Now, you upload the file using:

ftp.uploadSecure(@"Filepath", false)

Note: you can upload in non secured mode using ftp.upload().

Points of Interest

I learned how an SSL stream and the RAW FTP communication works between a client and an FTP server. Searching on the web, I found many who were stuck on the issue of SSL communication with an FTP server, so I hope this article will be of great help.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

kadaoui el mehdi
Architect
Belgium Belgium
in 2005, I started my career. Net and I could improve in this technology through the project WinFroms. Net 2.0 / MVC2 for "Nestle".

After obtaining my diploma MASTER "MBDS" from the University of Nice Sophia Anti-police, I left to Belguim to work as Expert .Net Analyst Developer.

Currently I specialize in architecture Asp.net to the lowest level.

Meanwhile I remain very active in the community. Net, I created the 1st community. Net Morocco "on Facebook and LinkedIn and twitter, called "Morocco .Net User Group (MONUG)"

Comments and Discussions

 
Question_sslStream.AuthenticateAsClient hangout PinmemberMember 1096598014-Mar-15 8:07 
QuestionException PinmemberMehraRaj25-Dec-14 19:01 
GeneralBeware and use with caution PinmemberSeva Zaslavsky11-Jul-14 3:03 
GeneralRe: Beware and use with caution PinmemberAntonio Ripa1-Aug-14 12:05 
SuggestionAnother library to try if you have problems with this one.... Pinmembergmagana29-Jan-14 14:37 
QuestionAplication freezing after login method PinmemberMember 194843914-Jan-14 9:45 
Questionsftp PinmemberKing Ravi Kumar14-May-13 3:13 
QuestionDoes anyone have an implemenation example ? PinmemberMember 979519322-Mar-13 9:24 
QuestionAn unknown, invalid, or unsupported option or level was specified in a getsockopt or setsockopt call PinmemberMember 982113318-Feb-13 9:26 
QuestionHow to run this program. PinmemberMember 982113318-Feb-13 9:05 
QuestionFTPS - Connecting to the server through proxy PinmemberMember 251419017-Jan-13 22:19 
QuestionWhy is the SslStream object stuff commented out? Is this truly FTP over SSL without that? Pinmemberandegre16-Aug-12 9:31 
QuestionDir not working with secure PinmemberBig D30-May-12 8:47 
AnswerAre you having issues uploading and downloading files? PinmemberMember 76555695-Apr-12 12:09 
The IBM FTP server I was using this class to access was freezing when trying to upload or download files. It froze on the _sslStream.AuthenticateAsClient function. The issue turned out to be the sequence of commands sent to the server. On the IBM FTP server you have to send the RETR/STOR commands first thing after creating the data transfer socket before you call the function to create the secure stream. I've edited the class a bit, but here are the revised upload and download functions I use that work with the IBM FTP server:
 
NOTE: The functionality to resume has been removed because our server doesn't support it. Also, you may notice the outDelegate. This is the function used to output. You can set it to any function that returns void and takes a string (Ex: Console.WriteLine).
 
        /// <summary>
        /// Upload a file to the server
        /// </summary>
        /// <param name="fileName">The file name (including path) of the local file to upload</param>
        /// <returns>True if successful, False otherwise</returns>
        public bool Upload(string fileName)
        {
            // If we aren't logged in already
            if (!loggedIn)
            {
                Login(); // Login
            }
 
            // Create the data socket and attempt to connect
            Socket cSocket = createDataSocket();
            isData = true;
 
            if (outDelegate != null)
            {
                outDelegate("Data Socket Connected: " + cSocket.Connected.ToString());
                if (appendNewLines)
                    outDelegate("\n");
            }
 
            // Send the store command to the server
            sendCommand("STOR " + Path.GetFileName(fileName));
 
            if (!(retValue == 125 || retValue == 150))
            {
                if (outDelegate != null)
                {
                    outDelegate("Error: Bad response from server during upload: " + reply);
                    if (appendNewLines)
                        outDelegate("\n");
                }
                return false;
            }
 
            // If we were able to secure the stream
            if (getSslStream(cSocket))
            {
                // Id the data socket is connected
                if (cSocket.Connected)
                {
                    byte[] bufferFile = null;
                    try
                    {
                        // Open the local file for reading
                        FileStream input = File.OpenRead(fileName);
                        if (outDelegate != null)
                        {
                            outDelegate("Uploading file " + fileName + " to " + remoteDir);
                            if (appendNewLines)
                                outDelegate("\n");
                        }
 
                        while (true)
                        {
                            bufferFile = new byte[BLOCK_SIZE];
 
                            int bytes = input.Read(bufferFile, 0, bufferFile.Length); // Fill the buffer with the file
                            dataStream.Write(bufferFile, 0, bufferFile.Length); // Write the buffer to the server using the secure stream

                            // If we read less bytes than the file had left, we reached the end of the file
                            if (bytes < bufferFile.Length)
                            {
                                break;
                            }
                        }
 
                        // Close the local file
                        input.Close();
 
                        if (outDelegate != null)
                        {
                            outDelegate("File successfully uploaded");
                            if (appendNewLines)
                                outDelegate("\n");
                        }
                    }
                    catch (Exception ex)
                    {
                        if (outDelegate != null)
                        {
                            outDelegate("Error uploading file: " + ex.Message);
                            if (appendNewLines)
                                outDelegate("\n");
                        }
                        return false;
                    }
                }
 
                // Close the secure stream
                dataStream.Close();
            }
 
            // If the socket is still connected, close it
            if (cSocket.Connected)
            {
                cSocket.Close();
            }
 
            // Read and check the reply
            readReply();
            if (!(retValue == 226 || retValue == 250))
            {
                if (outDelegate != null)
                {
                    outDelegate("Error: Bad response from server during upload: " + reply);
                    if (appendNewLines)
                        outDelegate("\n");
                }
                return false;
            }
 
            isData = false;
            return true;
        }
 
        /// <summary>
        /// Downloads a file from the server
        /// </summary>
        /// <param name="remFileName">Filename of the file on the server</param>
        /// <param name="locFileName">Filename (with path) of the local file</param>
        /// <returns>True if successful, False otherwise</returns>
        public bool Download(string remFileName, string locFileName = null)
        {
            // If we aren't logged in, do so now
            if (!loggedIn)
            {
                Login();
            }
 
            isData = true;
 
            // If the local file isn't set, default it to be the same name as the server's file name
            if (locFileName == null || locFileName.Equals(""))
            {
                locFileName = remFileName;
            }
 
            try
            {
                // Create or open the local file for writing
                FileStream output = new FileStream(locFileName, FileMode.OpenOrCreate, FileAccess.Write);
 
                // Create the data socket
                Socket cSocket = createDataSocket();
 
                // Send the retrieve command to the server
                sendCommand("RETR " + remFileName);
 
                if (!(retValue == 150 || retValue == 125))
                {
                    if (outDelegate != null)
                    {
                        outDelegate("Error: Bad response from server during download: " + reply);
                        if (appendNewLines)
                            outDelegate("\n");
                    }
                    return false;
                }
 
                // Secure the stream
                this.getSslStream(cSocket);
 
                if (cSocket.Connected)
                {
                    if (outDelegate != null)
                    {
                        outDelegate("Downloading file " + remFileName + " from " + remoteHost);
                        if (appendNewLines)
                            outDelegate("\n");
                    }
 
                    byte[] downBuffer = new byte[1024];
                    int len;
                    // Read the file from the server and write it to the local file
                    while ((len = dataStream.Read(downBuffer, 0, downBuffer.Length)) > 0)
                    {
                        output.Write(downBuffer, 0, len);
                    }
 
                    dataStream.Close();
                }
 
                // Close everything
                output.Close();
                if (cSocket.Connected)
                {
                    cSocket.Close();
                }
 
                // Read the reply
                readReply();
                if (!(retValue == 226 || retValue == 250))
                {
                    if (outDelegate != null)
                    {
                        outDelegate("Error: Bad response from server during download: " + reply);
                        if (appendNewLines)
                            outDelegate("\n");
                    }
                    return false;
                }
            }
            catch (Exception ex)
            {
                if (outDelegate != null)
                {
                    outDelegate("Error downloading file: " + ex.Message);
                    if (appendNewLines)
                        outDelegate("\n");
                }
                return false;
            }
 
            if (outDelegate != null)
            {
                outDelegate("Download Complete");
                if (appendNewLines)
                    outDelegate("\n");
            }
 
            isData = false;
            return true;
        }

GeneralRe: Are you having issues uploading and downloading files? Pinmembergmagana29-Jan-14 12:26 
QuestionIndex and length must refer to a location within the string.\r\nParameter name: length PinmemberMember 84911326-Mar-12 22:56 
QuestionNo port 990 PinmemberMember 855570311-Jan-12 8:02 
AnswerRe: No port 990 Pinmemberbob mourning2-Mar-12 3:49 
Questionneeds your helps PinmemberJacob P Yamarthi18-Oct-11 22:53 
AnswerRe: needs your helps PinmemberMember 76555695-Apr-12 11:57 
GeneralRe: needs your helps Pinmembervolax12-Feb-13 6:39 
QuestionUpload File - Nothing Happens PinmemberSergio Marchetti22-Aug-11 13:04 
AnswerRe: Upload File - Nothing Happens PinmemberMember 76555695-Apr-12 11:56 
QuestionCannot Upload File Pinmemberluis hernandez11-Aug-11 10:20 
AnswerRe: Cannot Upload File PinmemberMember 76555695-Apr-12 11:56 

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